Name: nerve signals that trigger muscle contraction
Uploaded: 2025-10-23T11:49:17.000Z
Duration: 1 min 15 s
Channel: JoVE

يبدأ تقلص العضلات الهيكلية الطوعية في الدماغ كجهد واع للفص الجبهي للقشرة الحركية الأساسية،قبل تفعيل خلية عصبية حركية ألفا تقع في القرن الأمامي للحبل الشوكي. تستمر الإشارة أسفل العصب وصولاًإلى ألياف عضلية محددة مثل العضلة ذات الرأسين،حيث تنهي إمكانيات الحركة تقاطعطات العصب العضلي،حيث تقوم الخلية الحركية بإنشاء اتصال متشابك مع الألياف العضلية وبتحريك إطلاق الناقل العصبي أستيل كولين"الذي ينشر عبر شق متشابك ويربط المستقبلات. ونتيجة لذلك،يصبح غشاء الليف العضلي أكثر نفاذية لأيونات الصوديوم،مما ينتج عنه المزيد من إمكانيات الحركة التي تنشر على طول سطحها الخارجي وأيضاًداخل الألياف العضلية عبر أنيبيب مستعرض وعرضي،يؤدي إلى إطلاق أيونات الكالسيوم من الشبكة الإندوبلازمية العضلية في اللييفات العضلية.إن إطلاق هذا الكالسيوم هذا يفعّل بروتين الميوسين ونشاط عبور ومراقبة تقصير العضل والتقلص.

ويب ، ر. كلينتون. "تقلص العضلات الملساء والاسترخاء". التقدم في تعليم علم وظائف الأعضاء 27 ، العدد 4 (1 ديسمبر 2003): 201-6. [<a href = "https://doi.org/10.1152/advan.00025.2003" target = "__blank" >المصدر</a>]

كو ، إيفانا واي ، وباربرا إي إيرليش. "الإشارات في تقلص العضلات". وجهات نظر كولد سبرينج هاربور في علم الأحياء 7 ، العدد 2 (فبراير 2015). [<a href = "https://doi.org/10.1101/cshperspect.a006023" target = "__blank" >مصدر</a>]

تقلص العضلات

في العضلات الهيكلية, يتم تحرير الأسيتيل كولين بواسطة أطراف عصبية في لوحة نهاية المحرك _ نقطة الاتصال المشبكي بين الخلايا العصبية الحركية وألياف العضلات. يسمح ربط الأسيتيل كولين بمستقبلاته على غمد الليف العضلي بدخول أيونات الصوديوم إلى الخلية ويطلق جهد فعل في الخلية العضلية. وهكذا ، تنتقل الإشارات الكهربائية من الدماغ إلى العضلات. بعد ذلك ، يقوم إنزيم أستيل كولينستريز بتفكيك الأسيتيل كولين لمنع التحفيز المفرط للعضلات.

 

الأفراد الذين يعانون من اضطراب الوهن العضلي الوبيل يطورون أجساماً مضادة لمستقبلات الأسيتيل كولين. هذا يمنع انتقال الإشارات الكهربائية بين الأعصاب الحركي والألياف العضلية ويضعف تقلص العضلات الهيكلية. يتم علاج الوهن العضلي الوبيل باستخدام الأدوية التي تثبط أستيل كولينستراز (مما يتيح المزيد من الفرص للناقل العصبي لتحفيز المستقبلات المتبقية) أو قمع جهاز المناعة (منع تكوين الأجسام المضادة).

<h4>تقلص العضلات السلس</h4>

على عكس العضلات الهيكلية ، فإن العضلات الملساء الموجودة في جدران الأعضاء الداخلية يعصبها الجهاز العصبي اللاإرادي وتخضع لانقباضات لا إرادية. يتوسط التقلص عن طريق التفاعل بين بروتينين خيطيين _ الأكتين والميوسين. يرتبط تفاعل الأكتين والميوسين ارتباطاً وثيقاً بتركيز الكالسيوم داخل الخلايا. استجابةً للناقل العصبي أو إشارات الهرمونات أو شد العضلات ، يدخل الكالسيوم خارج الخلية إلى الخلية من خلال قنوات الكالسيوم الموجودة على غمد الليف العضلي أو يتم إطلاقه داخل الخلايا من الشبكة الساركوبلازمية. داخل الخلية ، يرتبط الكالسيوم بالبروتين التنظيمي كالموديولين. ينشط مركب الكالسيوم والكالودولين بعد ذلك إنزيم الميوسين كيناز ذو السلسلة الخفيفة ، والذي يفسفر الميوسين ويسمح له بالتفاعل مع الأكتين ، مما يتسبب في تقلص العضلات.

 

في عضلات الهيكل العظمي ، يتم إطلاق الأسيتيل كولين بواسطة الأطراف العصبية في لوحة نهاية المحرك - نقطة الاتصال المشبكي بين المحرك ...

Education

JoVE Core

Biology

علم الأحياء

Human Biology

بيولوجيا الإنسان

Musculoskeletal System

الجهاز العضلي الهيكلي

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

Muscle Contraction

nerve signals that trigger muscle contraction

Nerve signals trigger muscle contraction in both skeletal and smooth muscle, but the two muscle types use different control systems. In skeletal muscle, the signal begins at the motor end plate, which is the synapse between a motor neuron and a muscle fiber. In smooth muscle, contraction is controlled by the autonomic nervous system and happens without conscious control.

In skeletal muscle, motor nerve terminals release acetylcholine. This neurotransmitter binds to receptors on the sarcolemma, the muscle cell membrane, and lets sodium ions enter the cell. That change starts an action potential in the muscle cell and carries the electrical signal from the brain to the muscle. The enzyme acetylcholinesterase then breaks down acetylcholine so the muscle is not overstimulated.

Myasthenia gravis shows what happens when this signaling step is disrupted. In this disorder, antibodies form against the acetylcholine receptor. As a result, the signal between the motor neuron and the muscle fiber is blocked, and skeletal muscle contraction is weakened. Treatment may include drugs that inhibit acetylcholinesterase or medicines that suppress the immune system.

Smooth muscle in the walls of internal organs contracts in a different way. Its contraction depends on the interaction between actin and myosin, two filament proteins. This process is closely linked to calcium levels inside the cell, which can rise after neurotransmitter or hormone signals or when the muscle is stretched.

Calcium can enter smooth muscle from outside the cell through calcium channels on the sarcolemma, or it can be released from the sarcoplasmic reticulum inside the cell. Once inside, calcium binds to calmodulin, a regulatory protein. The calcium-calmodulin complex activates myosin light chain kinase, which phosphorylates myosin and lets it interact with actin, causing contraction.

Nerve Signals That Trigger Muscle Contraction

nerve-signals-that-trigger-muscle-contraction

what is the skeletal system?

Human Skeleton: Bones, Cells, and Disease

The human skeleton is a living framework made of 206 bones in adults. Bones connect with cartilage, tendons, and ligaments. This system gives the body support, protects organs, and helps with movement and locomotion. The skeleton has two main parts: the axial skeleton and the appendicular skeleton. The axial skeleton has 80 bones and includes the skull, the vertebral column, and the rib cage. The cranium, or upper skull, has eight bones that enclose the brain, while the lower part of the skull...

bone structure

Inside a Long Bone

Inside a long bone, osseous tissue is organized into two main types: cortical bone and cancellous bone. A femur is a clear example of this structure. The bone also includes outer coverings and inner spaces that support growth, repair, and blood cell production. Cortical bone, also called compact bone, forms the dense outer layer along the diaphysis, or shaft. It is covered by the periosteum, a membrane with connective tissue, capillaries, and nerves. Beneath the cortical layer is the medullary...

joints

Types of Joints in the Human Body

Joints are the places where adjacent bones connect. They are also called articulations or articular surfaces. Joints help the body move and stay stable. Joints can be classified by structure or by function. Structural classification depends on the material that forms the joint and whether there is a space between the bones. By structure, joints are fibrous, cartilaginous, or synovial. Fibrous joints are connected by fibrous tissue and have no cavity between the bones. Because of this, they do...

bone remodeling

How Hormones Control Bone Turnover

Bone turnover is a continuous process in which old bone is broken down and new bone is built. Osteoclasts carry out bone resorption, and osteoblasts carry out bone formation. In adults, this balanced cycle helps maintain bone mass and calcium homeostasis. Mechanical stress can also stimulate turnover as part of normal maintenance and repair. Parathyroid hormone, or PTH, helps control blood calcium levels by increasing bone resorption when calcium is low. It is released from the parathyroid...

skeletal muscle anatomy

Muscle Fibers, Tendons, and Contraction

Skeletal muscle moves the body by pulling on bones through tendons. Tendons are the connective tissue that attaches skeletal muscle to bones. When skeletal muscles contract, they create voluntary movement. Skeletal muscle is wrapped in layers of connective tissue. The outer layer is the epimysium, which helps protect the muscle. Beneath it, the perimysium surrounds and groups fasciculi, which are bundles of skeletal muscle cells called myocytes. These cells are also called skeletal muscle...

classification of skeletal muscle fibers

Skeletal Muscle Fiber Speed and Energy

Skeletal muscle fibers can be grouped by how fast they contract and how they make ATP, the energy cells use for movement. These differences also shape their physical features. Most human muscles contain all three fiber types, but in different amounts. Slow oxidative fibers, also called slow-twitch fibers, appear red because they have many capillaries and high levels of myoglobin, an oxygen-storing protein. They also contain more mitochondria, which make ATP through oxidative phosphorylation,...

muscle contraction

Nerve signals trigger muscle contraction in both skeletal and smooth muscle, but the two muscle types use different control systems. In skeletal muscle, the signal begins at the motor end plate, which is the synapse between a motor neuron and a muscle fiber. In smooth muscle, contraction is controlled by the autonomic nervous system and happens without conscious control. In skeletal muscle, motor nerve terminals release acetylcholine. This neurotransmitter binds to receptors on the sarcolemma,...

cross-bridge cycle

Calcium Control in Muscle Contraction

Calcium control in muscle contraction depends on ATP, motor neurons, and the sliding action of actin and myosin. As a muscle contracts, the thin and thick filaments overlap more, and the sarcomere, which is the contractile unit of the muscle, becomes shorter. This process uses energy from ATP and happens in a repeating cycle at the molecular level. Myosin drives the movement of actin through a cross-bridge cycle. When ATP attached to the myosin head is hydrolyzed to ADP, myosin shifts into a...

motor units

How Motor Units Control Muscle Movement

Motor units control skeletal muscle movement. A motor unit includes one efferent motor neuron, which carries signals away from the central nervous system, and all of the muscle fibers it innervates. A single motor neuron can connect with multiple muscle fibers, but each muscle fiber is innervated by only one motor neuron. Lower motor neurons are the efferent neurons that control skeletal muscle, the most abundant type of muscle in the body. Their cell bodies are found in the spinal cord or...

the spinal cord

Spinal Cord Structure and Dermatomes

The spinal cord is the main nerve pathway of the central nervous system. It carries sensory signals from the body to the brain and motor signals from the brain to the body. It begins at the foramen magnum, the opening at the base of the skull, and extends to the level of the first or second lumbar vertebra. In cross-section, the spinal cord is cylindrical and contains both gray matter and white matter. The central canal lies in the middle and is a remnant of the lumen of the primitive neural...

nociception

Pain Signaling and Inflammation

Pain signaling begins when the body detects a harmful stimulus. Sharp objects, open flames, and corrosive chemicals can trigger this response. Sensory receptors called nociceptors, which sit on nerve endings, detect these noxious stimuli and use ion channels to turn them into electrical signals. Those electrical signals travel through sensory neurons to the brain, where they are experienced as pain. This warning system helps an organism avoid damage and stay safe. Pain is therefore an...

key terms and concepts

Learn how acetylcholine, calcium, and actin-myosin interactions drive skeletal and smooth muscle contraction, plus how myasthenia gravis disrupts signaling.

Nerve Signals That Trigger Muscle Contraction | JoVE K12

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Nerve Signals That Trigger Muscle Contraction

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